29. Torsade de Pointes
EKG Characteristics: Irregular wide-complex
tachycardia
The morphology, amplitude, and
axis of the QRS complexes cycle
through a sinusoidal pattern
No discernable P waves
40. Atrial Flutter
Most cases of atrial flutter are caused by a large reentrant circuit in the wall of the
right atrium
EKG Characteristics: Biphasic “sawtooth” flutter waves at a rate of ~ 300 bpm
Flutter waves have constant amplitude, duration, and
morphology through the cardiac cycle
There is usually either a 2:1 or 4:1 block at the AV node,
resulting in ventricular rates of either 150 or 75
bpm
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41. Unmasking of Flutter Waves
In the presence of 2:1 AV block, the flutter waves may not
be immediately apparent. These can be brought out by
administration of adenosine.
Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005.
46. Preexcitation
ECG Characteristics of WPW:
1. Short PR interval
2. QRS prolongation
3. Delta wave
The most common form of preexcitation is called Wolfe-Parkinson-
White (WPW) syndrome, in which a direct atrioventricular connection
allows the ventricles to begin depolarization while the standard action
potential is still traveling through the AV node.